There will be a new setting on the Advanced tab
"Enable to prevent double click on submit button."
it will be enabled by default.

This setting disables the Submit button after click, to prevent double
click on button. Also prevents going back and submit the form again.
Note: this setting is ignored if the "Are you sure?" popup for the
submit button is enabled, or when you have filled in the Submit button
input attributes setting with a "onclick" attribute.